Heat sink with integrated buss bar

ABSTRACT

The invention centers around a circuit board assembly having a heat sink with a buss bar integrally formed therein. The heat sink is provided between two parallel, opposed circuit boards. The buss bar is provided between the two circuit boards and is in electrical contact with circuit modules provided on both circuit boards. The buss bar is electrically insulated from both the circuit boards and the heat sink but electrically connected to the circuit modules.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to electrical circuit boards and, moreparticularly, to a circuit board assembly having a buss bar fordistributing electrical current to several circuit modules provided onthe circuit board and a heat sink for thermally conducting heat awayfrom the circuit modules.

2. Description of the Related Art

Circuit boards are typically made of an electrically insulating materialand have multiple circuit modules mounted thereon. It is known to usemultiple buss bars mounted on the front surface of the circuit board toconduct electrical current from a suitable source to multiple modulesmounted on the front surface of the circuit board. It is also known toprovide a heat sink adjacent the modules in order to thermally conductheat away from the circuit board in order to protect the modules fromthe high heat generated as a result of the current flow through themodules.

It is desirable to incorporate buss bars into a circuit board for theefficient distribution of current from a single source to the multiplemodules. Preferably, the number of buss bars would be minimized toreduce weight and material cost.

SUMMARY OF THE INVENTION

The heat sink with an integrated buss bar according to the inventionovercomes the problems of the prior art by permitting the utilization ofa single buss bar for supplying electrical current to a large number ofmodules of an electrical circuit while providing means for effectivelythermally conducting the heat generated in the electrical circuit awayfrom the modules of the circuit board.

In one aspect, the invention comprises an electric circuit boardassembly incorporating at least one circuit board, wherein multiplecircuit modules are provided on the board. A buss bar is used to conductelectrical current from a suitable source of power to each of thecircuit modules. The buss bar is provided between the two circuit boardsand has multiple terminals formed thereon which are electricallyconnected to the circuit modules on both the circuit boards. A heat sinkis also provided between the two circuit boards, and has at least oneaperture provided therein to receive at least one of the buss barterminals extending from the buss bar to one of the circuit modules ofthe second circuit board. The heat sink is adapted to thermally conductheat away from the circuit modules.

Preferably, the heat sink also has a depression formed in the frontsurface thereof wherein the buss bar is received, at least in part, inthe depression.

In another embodiment, the buss bar is electrically insulated from theheat sink and circuit boards.

In another aspect, the invention comprises an electrical circuit boardassembly incorporating two circuit boards wherein each board has atleast one circuit module provided thereon and each board has an outeredge. A buss bar is provided between the two circuit boards and hasmultiple terminals provided thereon. The terminals are electricallyconnected to the circuit modules on both the first and second circuitboards. A heat sink is also provided between the two circuit boardsimmediately adjacent to the buss bar. The heat sink extends outwardlyfrom the circuit boards and has an outer edge extending beyond the outeredge of the circuit boards. The outer edge is adapted to contact theframe of a supporting chassis to thermally conduct heat away from thebuss bar and circuit modules to the frame.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the drawings inwhich:

FIG. 1 is a perspective view of an electrical circuit boardincorporating the heat sink and buss bar according to the invention; and

FIG. 2 is an exploded, perspective view of the heat sink and buss barassembly according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and to FIGS. 1 and 2 in particular, acircuit board assembly 12 having an integrated heat sink and buss baraccording to the invention is shown. The circuit board assembly 12comprises first and second circuit boards 14, 16, respectively, providedparallel to and closely adjacent to one another. Each circuit board hasa plurality of circuit modules 18 provided adjacent thereto andelectrically connected thereto by conventional connections 45. Each ofthe modules 18 is electrically connected to a single buss bar 20 whichis in turn selectively connected to a conventional power source (notshown). The particular structure of the circuit modules 18 is notcritical to the invention and therefore will not be described in detail.In the preferred embodiment, the circuit board assembly is formed fromtwo circuit boards. It is within the scope of this invention to utilizea single circuit board or more than two boards.

A conventional power terminal 24 is provided on one end of the circuitboard assembly 12. The terminal 24 has a plurality of pins 26 providedthereon for providing suitable electrical connections. A conventionalsignal terminal 28 is also provided on the circuit board assemblyadjacent the power terminal. The signal terminal is electricallyconnected to the circuit modules 18 and adapted to conduct electricalsignals thereto.

A heat sink 30 is provided between the first and second circuit boards14, 16. As described further below, the heat sink is adapted tothermally conduct heat away from the circuit boards 14, 16 and modules18 provided thereon. The heat sink 30 is substantially planar and has afront edge 32, a rear edge 34 and a pair of opposed side edges 36, 38.The heat sink 30 further comprises a top surface 40, a bottom surface(not shown) and a depression, pocket or recess 42 provided in the topsurface 40 for receipt of the buss bar 20. Preferably, the depression 42is complementary to the shape of the buss bar 20 and has a sufficientdepth to receive at least a portion of, if not all of, the entirethickness of the buss bar 20 therein. Preferably, the circuit modules 18are mounted to the front and rear surfaces of the heat sink by aconventional thermally conductive adhesive (not shown). Module apertures44 are provided in the circuit boards 14, 16 so that the modules 18extend outwardly beyond the exposed surfaces of the circuit boards 14,16. The heat sink is preferably formed from aluminum. However, anythermally conductive material is suitable.

The buss bar 20 comprises a front edge 46, a rear edge 48, a pair ofopposed side edges 50, 52 and top 54 and bottom surfaces extendingbetween the several edges. A plurality of buss bar terminals 56, 58protrude laterally from the top and bottom surfaces, respectively, ofthe buss bar. The terminals are preferably integrally formed with thebuss bar. However, the terminals can be mounted to the buss bar byconventional methods including welding or brazing. As described furtherbelow, the several terminals are electrically connected to the circuitmodules 18 provided on the first and second circuit boards 14, 16.Preferably, the buss bar and terminals are formed from copper. However,any electrically conductive material can be utilized.

The buss bar 20 is received in the depression 42 and enclosed therein bya cover 60 which is secured to the heat sink 30 by a conventionaladhesive. Preferably, the buss bar 20 is electrically insulated from thecover 60 and heat sink 30 by conventional insulation means. In FIG. 2,the buss bar 20 is insulated from the cover 60 and heat sink 30 by apair of sheets of insulating film 62, 64 provided between the buss bar20 and the cover 60 and heat sink 30, respectively. Examples of suitablematerial for the insulating film include TEDLAR™ and KAPTON™.Alternatively, the buss bar or adjacent components, could beelectrically insulated by coating with a conventional epoxy powdercoating. The insulating film 62 and cover 60 have terminal apertures 66,68, respectively, formed therein which are adapted to receive the bussbar terminals 56. Similarly, the insulating film 64 and heat sink 30have terminal apertures 70, 72 which are adapted to receive the buss barterminals 58 protruding from the bottom surface (not shown) of the bussbar 20. The buss bar terminals 56, 58 extend through apertures 74 formedon the circuit boards 14, 16 such that the terminals are exposed andavailable for connection to the circuit modules 18.

The circuit modules 20 are electrically connected to the buss barterminals 56, 58 by conventional fasteners 78 which secure conventionalelectrical leads 80 of the modules 20 to the terminals 56, 58. Althoughthe preferred embodiment discloses terminals 56, 58 which protrudeoutwardly from the buss bar 20, it is certainly within the scope of theinvention to provide electrical conduits which protrude inwardly fromthe circuit modules 18 to contact the buss bar 20.

As seen in FIG. 1, a single buss bar 20 is utilized to distributeelectrical current to multiple circuit modules 18 on the first circuitboard 14. Similarly, multiple circuit modules 18 are provided on thesecond circuit board all of which can be electrically connected to thesame buss bar 20. In the preferred embodiment, 16 different circuitmodules, eight on the first circuit board 14 and eight on the secondcircuit board 16, are electrically connected to the buss bar 20.

As noted above, the first and second circuit boards 14, 16 are providedclosely adjacent to one another with the heat sink, buss bar 20 andcover 60 provided intermediate the two circuit boards 14, 16. The sideedges 36, 38 of the heat sink extend beyond the top and bottom sides 84,86 and 88 of the first and second circuit boards 14, 16. The side edges36, 38 of the heat sink 30 are adapted to contact the conventional rails(not shown) of the chassis which receive the circuit board and thermallyconduct the heat generated in the circuit board assembly 12 to thechassis. Conventional wedge clamps 90, 92 are provided on the top andbottom side edges 36, 38 of the heat sink for maximizing the contactpressure between the top and bottom edges of the heat 20 sink and thechassis rails. The wedge clamps 90, 92 comprise actuator levers 94, 96which are interconnected to translating shafts 98, 100 received inside acam housing 102, 104. As the actuator lever 94, 96 is rotated from therelaxed position to the engaged position as seen in FIG. 1, the shafts98, 100 translate thereby causing cam members provided inside the camhousing 102, 104 to slide with respect to one another thereby expandingthe cam housings 102, 104 laterally with respect to the heat sink 30 andcircuit board 14, 16. This lateral expansion causes the side edges 36,38 of the heat sink 30 and cam housings 102, 104 to occupy substantiallyall of the space of the conventional rail provided in the chassis.Therefore, maximum surface contact and pressure is achieved between theedges 36, 38 of the heat sink 30 and the chassis.

The electrical circuit board assembly according to the inventionutilizes a single buss bar to conduct electrical current to circuitmodules provided on two closely adjacent circuit boards. Because of thelarge amount of heat which will likely be generated by the modules, theheat sink is provided immediately adjacent the modules and adapted tothermally conduct heat away from the circuit modules. As noted above,the buss bar is preferably imbedded into the heat sink. Preferably, thecover which encloses the buss bar in the heat sink recess iselectrically insulated such that the buss bar is substantiallyencapsulated inside the thermally conductive heat sink. By enclosing thebuss bar and imbedding it into the heat sink, the buss bar iseffectively shielded from inadvertent contact by individuals or looseobjects in and around the circuit board assembly.

Another advantage of the structure according to the invention is theability to use a single buss bar and heat sink for two opposed, closelyadjacent circuit boards. An electrical circuit assembly according to theinvention effectively combines two circuit boards and modifies thestructure of the heat sink and buss bar such that only a single buss barand heat sink can be utilized for two different circuit boards. Thisresults in material cost savings and weight reduction.

Still another advantage of the structure according to the invention isthe adaptability of the structure. For example, if a buss bar isimbedded between a single circuit board and a heat sink, this singlecircuit board assembly could be easily modified to attach a secondcircuit board thereto and utilize the same buss bar by merely securingthe second circuit board to the heat sink side of the original structureand electrically connecting the modules of the second board to the bussbar.

Reasonable variation and modification are possible within the spirit ofthe foregoing specification and drawings without departing from thescope of the invention.

The embodiments for which an exclusive property or privilege is claimedare defined as follows:
 1. In an improved electrical circuit boardassembly comprising a first circuit board having a front surface and arear surface, a second circuit board having a front surface and a rearsurface, the circuit boards being provided parallel to one another suchthat the rear surfaces are opposed and adjacent to one another, and aplurality of circuit modules provided on at least one of the surfaces ofthe first and second circuit boards, the improvement comprising:a bussbar provided intermediate the first and second circuit boards andadjacent to the rear surface of the first circuit board, the buss barbeing electrically connected to at least one of the circuit modulesprovided on the first circuit board and at least one of the circuitmodules provided on the second circuit board; a heat sink providedintermediate the first and second circuit boards and adjacent to boththe buss bar and the rear surface of the second circuit board, the heatsink being adapted to thermally conduct heat from the buss bar andcircuit modules away therefrom and comprising front and rear surfaces;and a cover provided on the front surface of the heat sink, the coverhaving at least one aperture formed therein for receipt of an electricalconnection extending between the buss bar and at least one of thecircuit modules of the first circuit board, so that the buss bar can beelectrically connected to circuit modules provided on both the first andseconds circuit boards.
 2. An improved electrical circuit board assemblyaccording to claim 1 wherein eight apertures are formed in the cover andeight circuit modules are provided on the first circuit board and areelectrically connected to the buss bar through eight electricalconnection conduits extending through the eight apertures between thebuss bar and the cover.
 3. An improved electrical circuit board assemblyaccording to claim 1 wherein the cover, in cooperation with the heatsink, substantially encloses the buss bar.
 4. An improved electricalcircuit board assembly according to claim 1 and further comprisinginsulating material provided between the cover and the buss bar suchthat the buss bar and heat sink are electrically insulated from oneanother.
 5. An improved electrical circuit board assembly according toclaim 4 and further comprising insulating material provided between theheat sink and the buss bar such that the buss bar and heat sink areelectrically insulated from one another.
 6. In an improved electricalcircuit board assembly comprising a first circuit board having a frontsurface and a rear surface, a second circuit board having a frontsurface and a rear surface, the circuit boards being provided parallelto one another such that the rear surfaces are opposed and adjacent toone another, and a plurality of circuit modules provided on at least oneof the surfaces of the first and second circuit boards, the improvementcomprising:a buss bar provided intermediate the first and second circuitboards and adjacent to the rear surface of the first circuit board, thebuss bar being electrically connected to at least one of the circuitmodules provided on the first circuit board and at least one of thecircuit modules provided on the second circuit board; a heat sinkprovided intermediate the first and second circuit boards and adjacentto both the buss bar and the rear surface of the second circuit board,the heat sink being adapted to thermally conduct heat from the buss barand circuit modules away therefrom; and a cover provided on the frontsurface of the heat sink, the cover having at least one aperture formedtherein for receipt of an electrical connection extending between thebuss bar and at least one of the circuit modules of the first circuitboard, so that the buss bar can be electrically connected to circuitmodules provided on both the first and seconds circuit boards; the heatsink comprising eight apertures and eight circuit modules are providedon the second circuit board and are electrically connected to the bussbar through eight electrical connection conduits extending through theeight apertures between the buss bar and the heat sink.
 7. An improvedelectrical circuit board assembly according to claim 6 wherein eightcircuit modules are provided on the first circuit board and electricallyconnected to the buss bar.
 8. An electrical circuit board assemblycomprising:a first circuit board having a front surface, a rear surfaceand at least two circuit modules electrically connected to at least oneof the front and rear surfaces; a buss bar provided adjacent the rearsurface of the first circuit board, the buss bar having a plurality ofterminals provided thereon which are electrically connected to circuitmodules on the first circuit board; and a heat sink having front andrear surfaces provided adjacent the buss bar such that the buss bar isintermediate the heat sink and rear surface of the first circuit boardand the heat sink is thermally connected to the circuit modules suchthat the heat sink is adapted to thermally conduct heat away from thecircuit modules; and a cover provided on the front surface of the heatsink, the cover having at least one aperture formed therein receiving atleast one terminal extending from the buss bar to at least one of thecircuit modules of the first circuit board, so that the buss bar can beelectrically connected to circuit modules provided on both the front andrear surfaces first circuit board.
 9. An electrical circuit boardassembly according to claim 8 wherein the cover, in cooperation with theheat sink, substantially encloses the buss bar.
 10. An electricalcircuit board assembly according to claim 8 and further comprisinginsulating material provided between the cover and the buss bar suchthat the buss bar and heat sink, are electrically insulated from oneanother.
 11. An electrical circuit board assembly according to claim 10and further comprising insulating material provided between the heatsink and buss bar such that the buss bar and heat sink are electricallyinsulated from one another.
 12. An electrical circuit board assemblycomprising:first and second circuit boards, each having at least onecircuit module provided thereon; a buss bar provided intermediate thetwo circuit boards, the buss bar having a plurality of terminalsprovided thereon which are electrically connected to circuit modules onboth the first and second circuit boards; a heat sink providedintermediate the two circuit boards, the heat sink being thermallyconnected to the circuit modules and adapted to thermally conduct heataway from the circuit modules, the heat sink having at least oneaperture provided therein for the receipt of at least one buss barterminal extending from the buss bar to at least one of the circuitmodules of the second circuit board and a depression formed in a frontsurface thereof, the depression being adapted to receive at least aportion of the buss bar therein; insulating material provided betweenthe heat sink and buss bar such that the buss bar and heat sink areelectrically insulated from one another; a cover provided on the frontsurface of the heat sink, the cover having at least one aperture formedtherein for receipt of at least one terminal extending from the buss barto at least one of the circuit modules of the first circuit board; andinsulating material provided between the cover and the buss bar suchthat the buss bar and heat sink are electrically insulated from oneanother.